The invention relates to establishing a packet communications session having a quality of service in a communications system.
Mobile communications systems, such as cellular or personal communications services (PCS systems), are made up of a plurality of cells. Each cell includes a radio base station, with each base station connected to a mobile switching center that controls processing of calls between or among mobile units or mobile units and wireline units tied to a public switched telephone network (PSTN).
Traditionally, mobile communications systems have been implemented as circuit-switched networks. In a circuit-switched network, a line between two end points of (e.g., two mobile units) is occupied for the duration of the connection between the end points. Such a connection is optimum for communications that are relatively continuous, such as speech. However, data networks such as intranets and the Internet use packet-based connections, in which communications between nodes on a link is by data packets. In such data networks, each node occupies the communications link only for as long as the node needs to send or receive a data packet.
Several packet-based wireless protocols have been proposed to provide more efficient connections between a mobile unit and a packet-based data network, such as Internet Protocol (IP) networks. One such protocol is the General Packet Radio Service (GPRS) protocol, which complements existing GSM (Global System for Mobile) communications systems. Other technologies that build upon GPRS are the Enhanced GPRS (EGPRS) technology (also referred to as Enhanced Data Rate for Global Evolution or EDGE) and EGPRS Compact (or EDGE Compact) technology, which offer higher data rates and complement GSM and IS-136 systems. Packet-based communications, such as IP communications, can thus be communicated over a wireless infrastructure enabled for such packet services. A mobile unit that is “packet-enabled” can thus more efficiently access traditional wired packet-based networks, including the Internet and local area networks (LAN) and wide area networks (WAN).
With the increased capacity and availability of packet-based data networks, the types of services that are available over such networks have increased. Traditional forms of communications across packet-based data networks include electronic mail, file transfer, web browsing, and other exchanges of digital data. However, more recently, audio and video communications (e.g., voice communications, video conferencing, multicast of multimedia data) have become possible. Voice communications over packet-based data networks are unlike voice communications in a conventional PSTN system, which provides users with dedicated, end-to-end circuit connections for the duration of each call. Voice and other forms of streaming data sent over a packet-based data network have to share the network bandwidth with conventional non-streaming data.
In a packet-based data network, such as an IP (Internet Protocol) network, transmission speeds of the various packets may vary widely depending on the usage of data networks over which the data packets are transferred. During periods of high usage of data networks, delays on the transfer of voice or other streaming data packets may cause poor performance of such communications. Voice data packets that are lost or delayed due to inadequate or unavailable capacity of data networks may result in gaps, silence, and clipping of audio at the receiving end.
To enhance communications that involve streaming data (such as voice or video conferencing) over data networks, a Resource Reservation Protocol (RSVP), as described in Request For Comments (RFC) 2205, entitled “Resource Reservation Protocol (RSVP),” dated Sep. 19, 1997, has been proposed to identify and reserve resources for traffic over a data network. By reserving such resources along nodes in the path of communications, some level of quality of service (QoS) may be provided to a user to enhance the user's experience in using the data network for various types of communications, including communications of audio and/or video data.
A node, whether fixed or mobile, may have various applications that provide for different types of communications over the data network. For example, communications such as electronic mail and web browsing may have low QoS requirements, whereas communications such as audio or video conferencing may have high QoS requirements. Thus, because of the different possible types of communications, support for multiple concurrent flows with different QoS requirements may be needed. A QoS profile may be defined in a Packet Data Protocol (PDP) context. A primary PDP context may be associated with an IP address of the mobile node. To support multiple QoS flows per IP address, one or more secondary PDP contexts or PDP sub-contexts may be created for the mobile node. Given a primary PDP context, a mobile node can activate multiple secondary PDP contexts with different QoS profiles as and when required.
The end points of a packet-based communications session may include a mobile unit linked to a packet-based wireless network and a terminal connected to a circuit-switched network, such as the PSTN. To enable such a communications session, a media gateway is provided between the packet-based wireless network and the circuit-switched network. The media gateway performs the translation between packet-based signals and circuit-switched signals. Although QoS is defined for packet-based networks, whether wired or wireless, QoS is not available in circuit-switched networks.
A need thus exists for a mechanism and method to provide for QoS in communications sessions between mobile units linked to packet-based wireless networks and terminals connected to a circuit-switched network.